Molecular alloys formed by solid-state vitrification

Abstract

A new example of solid-state vitrification for trehalose from its crystalline sample is reported. DSC experiments on vitrified trehalose clarified the heat effects associated with glass transition, crystallization, and fusion, respectively. Increases in the glass transition temperature T g and the enthalpy of crystallization with the milling time that have commonly occurred in solid-state vitrification of molecular crystals was observed also in trehalose. Mechanical milling on several mixtures of trehalose and sucrose, both being geometrical isomers of disaccharides C 12H 22O 11, produced a series of molecular alloys with T g value varying monotonously with the composition. Observation of only a single T g in each solid indicated that the two component molecules mixed on a molecular level to exhibit a sole process for structural relaxation. Formation of other molecular alloys of trehalose with tri- O-methyl-β-cyclodextrin and glucose is also discussed. The former was totally miscible over the whole composition range, while the latter was partially miscible.